The comparison studies of photosynthetic characteristics and protective enzymes of Caragana microphylla and Caragana stenophylla

MA Cheng-Cang~(1,2), GAO Yu-Bao~(1*), WANG Jin-Long~1, GUO Hong-Yu~1, NIE Li-Li~1, ZHAO Juan~1 (1.College of Life Science, Nankai University, Tianjin 300071,China; 2. Department of Biology, Huaibei Coal Normal College, Huaibei 235000, China).  

The photosynthetic characteristics and protective enzymes of Caragana microphylla——a typical species of pinnately compound leaf group, and Caragana stenophylla —— a typical species of pseudo-palmately compound leaf group, were compared and studied in this paper, in order to understand their adaptation mechanism to its habitat and to provide experimental evidence for specific evolution of genus Caragana. The research of photosynthetic characteristics showed that light compensation point (217 μmol photon/(m~2·s)), light saturation point (1107μmol photon/(m~2·s)) and optimum temperature for photosynthesis (25.65℃) of C. microphylla were all lower than those of C. stenophylla (light compensation point: 342μmol photon/(m~2·s); light saturation point: 1444μmol·photon/(m~2·s); optimum temperature for photosynthesis: 32.89℃). The C. microphylla exhibited a higher photosynthesis rate at lower temperature and lower light intensity. The net photosynthesis rate of C. microphylla rose as air humidity increased while C. stenophylla reached its maximum net photosynthesis rate at air humidity of 80%~90%. These suggested that a photosynthetic system of C. stenophylla adapted better to higher temperature, more intensive radiation and more arid environment than that of C. microphylla, and C. microphylla could use low radiation more effectively. The photosynthesis rate and LUE of C. stenophylla were higher than those of C. microphylla after noon, which suggested that water retention of C. stenophylla was superior to that of C. microphylla. The fact that the daily average value of LUE of C. microphylla(8.17mmol CO_2/mol photon)was more than that of C. stenophylla (7.08 mmolCO_2/mol photon) enabled C. microphylla to exhibit better adaptation to lower radiation. These photosynthetic characteristics of the plants adapted to the light, temperature and humidity conditions of these plants own habitats. In terms of photosynthetic characteristics, C. stenophylla favored living in an environment of higher temperature, more intensive light radiation and less rain than C. microphylla, which might explain the present distribution characteristics of these two species of plants. There were not significant differences between C. stenophylla and C. microphylla in chlorophyll content and the ratio of chlorophyll a to chlorophyll b, which revealed that they take the variation of the chlorophyll function —— photosynthetic characteristics but not chlorophyll content as an adaptation strategy to the environment. The comparison of stress resistance showed that C. stenophylla had higher POD and SOD activities, resulting in the free radical content, membrane lipid peroxidation (MDA content) and the permeability of the plasma membrane was lower than those of C. microphylla. This was an important characteristic of C. stenophylla adaptation to the environment of drought, high temperature and intensive light radiation. The proline content in the leaf cell of C. stenophylla was lower than that of C. microphylla where the water status of C. stenophylla distribution region was significantly lower than that of C. microphylla distribution region. This demonstrated that C. stenophylla adapted to arid environment better than C. microphylla.From this study, we arrived at two main conclusions: (1) Plant of genus Caragana adapts to light, temperature, and humidity environments by means of the variation of photosynthetic characteristics and protective enzymes systems; (2) The typical species of the pseudo-palmately compound leaf group, C. stenophylla, adapts to arid, high temperature and intensive radiation environments better than the typical species of the pinnately compound leaf group, C. microphylla. These results provide proof of the view that the pinnately compound leaf group is the basic species and pseudo-palmately compound leaf group is the comparatively evolved species.

【Key Words】： C. microphylla C. stenophylla photosynthetic characteristics protective enzymes chlorophyll content environmental adaptation specific evolution pinnately compound leaf group pseudo-palmately compound leaf group
【Fund】： 国家重点基础研究发展规划资助项目 ( G2 0 0 0 0 1860 1)~~
【CateGory Index】： Q948.1

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